Working machines, in particular forestry equipment and forest machines, e.g. a harvester and a forwarder, have an articulated boom and a tool attached to the boom. The tool can be e.g. a harvester head, a felling head, a harvesting and processing head, or a log grapple. The tool can be used e.g. to cut standing trees, to process felled trees or to grab objects, such as logs or tree trunks. When using such a tool, it is moved under the control of an operator of the work machine to a desired position mainly by controlling the position of the boom and moving the tool with the boom.
The hydraulic control systems for controlling e.g. the boom are dimensioned for a predetermined highest maximum pressure requirement. In the previously known hydraulic control systems for e.g. the working machines with a boom, the force and especially the available net force for lifting loads or moving the boom can be perceived as too small when the boom is extended or the horizontal reach of the boom is reaching its maximum. On the other hand, the available net force for lifting loads or moving the boom can be perceived as unnecessarily high when the boom is retracted or the horizontal reach of the boom is reaching its minimum. In the former case it may be impossible to perform selected work functions and in the latter case hydraulic energy is wasted or the boom must be constructed unnecessarily durable to take long-term overload. Thus, there are conflicting design requirements because the available net force should be high and the boom should be constructed with long reach and a light structure.